Micky wrote:

> When setting system-name to nil (should that be allowed?), Emacs forgets
> how to delete the lock files '.#.*' and all subsequent startups complain
> about lockups by old dead PIDs.

I think this is a "don't do that, then".
If Emacs fails to set system-name, that is a bug.
If you actively set system-name to nil, that's just shooting yourself
in the foot.
Why did you want to do that, and what made you think it would work?